Heliometer

A heliometer is a really cool telescope that helps scientists measure the size of stars. Imagine you want to measure how big your friend's head is, but you can't just walk up to them with a ruler! So, you use a heliometer, which is like a super powerful telescope that can look at stars that are very far away.

Now, the cool thing about a heliometer is that it has two lenses that can move closer or farther apart. This is like when you move your hands together or apart to see how big something is. Scientists use the heliometer to observe a star and then move the lenses closer or farther apart until they see two images of the star.

Once they have two images, they measure the distance between them. This measurement helps the scientists calculate the size of the star they are looking at. It's kind of like measuring your friend's head by looking at two photographs of them and measuring the distance between their ears in both pictures.

Overall, a heliometer is a powerful tool that helps scientists study stars and learn more about the universe!